Project North is the orientation that plans will by default appear on sheets.
You can change the orientation of individual views on sheets by:
changing the View parameter Rotate View on Sheet.
or creating a Scope box and rotating it. See TIPS & TRICKS > SHEET VIEWS and TITLE BLOCKS > ROTATE VIEWS
In Revit Project North is the base orientation. A bit like WCS (World User Co-ordinate System) in AutoCAD, but more like older versions where there were no customizable UCSs.
The only customizable UCS in Revit is True North. When you rotate True North you are just changing some values, setting a new UCS.
But when you rotate Project North, you are actually ROTATING EVERYTHING IN THE PROJECT.
This has consequences:
elevations and sections are NOT rotated, so will have to recreated.
linked Revit files will not have their Project North changed
linked CAD files will not be rotated (but will correct themselves when reloaded).
IT IS NOT RECOMMENDED TO ROTATE PROJECT NORTH IF A PROJECT IS WELL ADVANCED.
If your project has just started with no, or very few, elevations and/or sections the procedure is:
1. Close all but the Project file you want to rotate project north in.
Having multiple instances of Revit with linked files open confuses Revit, and will confuse you. Changes will not necessarily propagate between files as you expect.
2. Make sure you know the insertion point of any linked Revit files. Create something to mark the location if you need to (e.g. Detail lines).
All linked Revit files will need to be Removed and placed again. You need to know where to put them when you insert them again.
3. If you are rotating OTHER than 90 or 180 degrees draw a reference plane where you want Project North to be.
The command requires you to select a line to become the new Project North.
4. Do the command - Manage > Position > Rotate Project North
If 90 or 180 degrees just select the one you want.
If another angle pick Align selected line or plane. If this doesn't rotate to where you want, repeat and use one of the 90 or 180 degrees commands to get it right.
5. Linked CAD files
Linked CAD files won't appear to rotate, but will when reloaded.
Either reload them manually, or just leave them. They will reload themselves when you next open the project file.
6. Fix or delete & remake Elevations and Sections.
If you rotated exactly 90 or 180 degrees you can just rename your elevations.
Note that any annotation will be wrong because it will be in the wrong view. You can copy and paste annotation between views.
Sections will not only face the wrong way but will most likely bisect at the building at a different place. Annotation will also be wrong.
If you rotated anything other than 90 or 180 degrees you must DELETE ALL ELEVATIONS and SECTIONS. Although model objects may appear OK if you try and dimension in these views Revit is likely to crash.
7. Fix linked Revit files - Save current file, Close and Open first linked Revit file.
If you want linked Revit files to have the same Project North you will need to repeat all the steps above in each linked file.
8. Remove and re-Insert Revit linked files.
Open main file plus each file used as a link, one at a time.
Remove all linked Revit files. Insert them again. UNLOADING and RELOADING won't work.